1. Field of the Invention
The embodiments discussed herein relate to a trimming apparatus.
2. Background of the Related Art
In general, manufacturing variations result that electric properties of circuit components, such as ICs (Integrated Circuits), deviate from their standard values. The deviation beyond a tolerable value would cause an error and affect circuit operation. Consequently, in manufacturing semiconductor devices, trimming is performed to correct deviations from the standard values of electric properties.
In a trimming circuit, usually a bit value is set in a trimming object by cutting a prescribed fuse with a signal inputted from a pad. In this application, “cutting” a fuse refers to causing the fuse to blow.
Conventionally, there has been proposed a technique of creating, prior to cutting a fuse within ICs, a state simulating the fuse being cut so as to allow estimation of the result of fuse cutting.
Japanese Laid-open Patent Publication No. 05-63090
Japanese Laid-open Patent Publication No. 2010-267922
Some conventional trimming circuits do not allow estimation of an after-fuse-cutting state before the fuse is actually cut. Some electric properties may not necessarily fall within their standards after fuse cutting, and therefore failing to estimate the after-fuse-cutting state before cutting the fuse may result in a problem of reduced manufacturing yield rate (percentage of non-defective products among those released from the production line).
Meanwhile, in a trimming circuit of the above literatures, an after-fuse-cutting state may be preliminarily estimated by processing input data coming from a pad through a shift register and a selector. In the configuration of the trimming circuit in the above literatures, however, there exists a problem that an increase of bit width to be set in a circuit to be trimmed causes the number of pads, i.e., external input terminals to increase, accompanied with an increase of chip area as well.